Cerebrospinal Fluid Apolipoprotein E Levels in Delirium

BACKGROUND/AIMS Delirium and the apolipoprotein E ε4 allele are risk factors for late-onset Alzheimer disease (LOAD), but the connection is unclear. We looked for an association. METHODS Inpatients with delirium (n = 18) were compared with LOAD outpatients (n = 19), assaying blood and cerebrospinal fluid (CSF) using multiplex ELISA. RESULTS The patients with delirium had a higher Confusion Assessment Method (CAM) score (5.6 ± 1.2 vs. 0.0 ± 0.0; p < 0.001) and Delirium Index (13.1 ± 4.0 vs. 2.9 ± 1.2; p = 0.001) but a lower Mini-Mental State Examination (MMSE) score (14.3 ± 6.8 vs. 20.8 ± 4.6; p = 0.003). There was a reduction in absolute CSF apolipoprotein E level during delirium (median [interquartile range]: 9.55 μg/mL [5.65-15.05] vs. 16.86 μg/mL [14.82-20.88]; p = 0.016) but no differences in apolipoprotein A1, B, C3, H, and J. There were no differences in blood apolipoprotein levels, and no correlations between blood and CSF apolipoprotein levels. CSF apolipoprotein E correlated negatively with the CAM score (r = -0.354; p = 0.034) and Delirium Index (r = -0.341; p = 0.042) but not with the Acute Physiology and Chronic Health Evaluation (APACHE) index, or the MMSE or Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE). CONCLUSION Reduced CSF apolipoprotein E levels during delirium may be a mechanistic link between two important risk factors for LOAD.